Regular samples were required of the feed to a copper processing plant, having a
ID: 288941 • Letter: R
Question
Regular samples were required of the feed to a copper processing plant, having a copper content of about 9%. The confidence level of estimation was required to be 0.1 % Cu at 2 standard deviation. The liberation size of the Cu mineral (chalcocite) in the ore was determined to be 75 um. A sieve analysis showed that the 95% pass size and 5% passing size were 2.5 cm and 50 m respectively Determine the minimum mass of sample required to represent the ore. Given; the density of chalcocite is 5600 kg/m3 and the density of the gangue is 2500 kg/m3Explanation / Answer
Given that mass per cubic meter of ore is 8100 kg.
The size at which 95% of the particles could pass through was 2.5 cm. Rest of the particles (5%) had a size of 50 m.
The size up to which the crushing of ore took to separate particles containing Cu was 75 m (liberation size). So, 5% of the sample was not considered as the size was less than the liberation size. This means that 7695 kg of ore (95% of 8100) must have been considered for separating Cu from gangue.
95% of the ore (two standard deviations) was required to have 0.1% of Cu. So, 95% of the ore mass represented viable quantities of Cu.
Thus, the minimum amount of sample required to represent the ore = 7695 kilograms.